Method and apparatus for grinding



March 13, 1928..

W. E. HOKE METHOD AND APPARATUS FOR GRINDING Filed Dec. 23. 1924 4Sheets-Sheet 1 March 13, 1928. 1,662,672

W. E. HOKE METHOD AND APPARATUS FOR GRINDING Filed Dec. 23. 1924 4Sheets-Sheet 2 gmanlot;

W. E. HOKE METHOD AND APPARATUS FOR GRINDING March 13, 1928.

Filed Deo. 25. 1924 4 ShetS-Sheeb 3 March 13, 1192-8.

' w. E. HOKE' METHOD AND APPARATUS FOR GRINDING Filed Dec. 23. 1924 4Sheets-Shee 4 W1K. j

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Patented Mar." 13, 1928.

UNITED STATES 1,662,672 PATENT OFFICE.

WILLIAM E. HOKE, F BALTIMORE, lMARYLAND. A

METHOD AND APPARATUS FOB GBINDING.

Application tiled December 23, 19274. Serial No. 757,740.

My invention relates to a method and apparatus for grinding or abrading,prefer-- a ing articles of this type, after they have been hardened, toa highy accurate predetermined inal form and polish.

My invention is a new application of the method described in my UnitedStates Patent No. 1,486,338, patented March 11, 1924, in which, I havedescribed the method of making a multiplicity of identical articles byrepeated lapping and systematic interchange of the relative position ofthe articles. This saine system or mode of operation is utilized infinishing articles of the kind above described, but is based on what Ibelieve to be an entirely new-principle or idea which consists infinishing the articles by lapping betweencurved surfaces of revolution.These lapping surfaces may be considered as generated by the revolutionof a line about" a rectilinear axis not in the plane of the lgeneratrixand are, when the generating line 1s straight, portions of surfaces ofhyperboloids of revolution, and have the characteristic that through anypoint of they surface two rectilinear elements of the surface may bedrawn.

The articles to be ground or lapped, whether cones or cylinders, willtherefore be abraded or ground by what is substantially a line contactbetween the surfaces of the article being groundA and the surface of thelap.

While I have referred to cylindrical and conical articles, thegenerating line of which is straight, my invention is also applicablefor the finishing of articles having curved generating lines, eitherconcave or convex, the articles being spool shaped or barrel shaped; orthe invention may also be applied to the finishing of articles havingother more or less curved outlines, as long as the surfaces of sucharticles are surfaces of revolution.

The invention will be readily understood by reference to theaccompanying description and drawings in which Fi 1 is a sectionalelevation on plane A- of Fig. 2 of one form of device;

Fig. 2 is a plan of Fig. 1;

Fig. 3 is a detail;

Fig. 4 is a partial plan of one form of work holder;

5 is an elevation of Fig. 4;

Fig. 6 is a partial plan of another form of work holder;

F 7 is an'elevation of Fig. 6;

Figs. 8, 9, 10 and 11 are diagrams; and

Figs. 12, 13, 14 and 15 show in section details of lap construction.

Referring to Fig. 1 in which the machine is diagralnniaticallyillustrated, 1 is a nonrevoluble lap of cast iron or other suitablematerial; 2 is a like cooperating lap resting upon the articles beingground, but is preferably free to move in any direction, or in otherwords, is freely floating. The lap 2 is provided with upstanding pins 3,4 having an upper hooked portion as shown in the detail, Fig. Looselyengaging these pins is a cross-bar or dog 5 carried by the shaft 6 whichis rotated by any suitable mechanism, such as the spindle of a drillpress.

` Either the non-rotatable or the revoluble lap may be freely floating.

The articles to be lapped such as cylinders or coned rollers 7, are heldin proper position by means of a work holder or spider 8, this spiderbeing free to rotate on an axially located pin 9, the spider beingspaced from the lower lap l by means of a washer or boss 10. This spideror work holder serves to maintain the articles 7 with their axes at anangle to the vertical plane passing through the axis of rotation of theshaft 6. The lapping surfaces 8 and 9 are, in this particular instance,doubly ruled warped surfaces generated by lines which are at an angle tothe horizontal plane and also at an angle to the vertical plane in whichis the axis of revolution of the lap.

This will be apparent in accordance with well known principles ofdescriptive geometry from the diagram Fig. 8, since the revolution ofthe line 8-8 about the axis 6 will generate one hyperboloidal surface ofrevolution, while the line 9-9 will generate a second hyperboloidalsurface. If the article being lapped is a cylinder, then the two warpedsurfaces will be generated by parallel lines.

The characteristics of such warped surfaces are shown in Figs. 9, l0 and11, in

f which Fig. 9 is a meridional or axial section on plane A-B of thelower lap, the` lines 8", 8, being on this plane portions of a.

hyperbole, while on a properly taken section the lines 8b, 8b arestraight lines.

The article being lapped has its axis in a plane passing through thesegenerating lines on the upper and lower laps, and therefore is engagedby these cooperating lapping surfaces with what is theoretically, and inpractice substantially, a line engagement. It will be noted that, asshown in Fig. 1, the working space between the surfaces 8 and 9 isupwardly inclined, although, as will be pointed out later, thisparticular arrangement is notiessential to my invention.

As shown in Fig. 15, one of the lapping surfaces may have a planesurface, while the other cooperating surface is a hyperboloid surface ofrevolution.

In operation, a multiplicity of the articles to be lapped, arranged inthe work holder (see Fig. 2) are placed in position on the lowernon-revoluble lap and the upper rotatable freely floating lap is thenplaced in position resting on the articles. As the upper lap is rotated,the articles will be moved around in the working space between the twolapping` surfaces and will be given at the same time a movement ofrotation about their individual axes and a longitudinal movement alongthose axes, or some combination of these movements, as the result ofwhich they are not simply rolled around, but are subjected to a grindingaction. At the outset the upper llap will rest upon those articles whichare of greater dimension than other articles in the group, and thedimensions of these particular articles will gradually be reduced untilthe upper lapping surface bears upon a larger number of these separatearticles. The articles-are then symmetrically transposed according tothe method described in my Patent No. 1,486,388, and again subjected tothe lapping operation; and this alternate lapping and transposition iscontinued until each one of the articles is brought to its predeterminedfinal exactly accurate size.

When the articles being lapped are so arranged as to have substantiallyline contact, as above described, with the lapping surfaces, thearticles are ground along their straight line generatrices. If theiraxes are yinclined still further in either direction, the

surfaces will be ground with correspondingly curved surfaces.

So also, if the generating lines are curved, articles of a generalconvex or barrel shaped or of a concave or spool shaped cross-sectioncan be ground.

The working space between the two laps is most conveniently arranged asshown in Fig. 1, but the opening may be peripherally arranged.

The upper lap 2 has at its periphery shoulders 12, 1Q, which hear uponthe upper or butt ends of the articles, the weight of the upper lap thustending to force the article downwardly and inwardly, so that sufficientgrinding press'ure' is applied, while at the same time the periphery ofthe butts of the articles is dubbed off.

The grinding surfaces of these shoulders may be either plane or curvedto fit the work.

As shown in Fig. 1Q, the lower lap may also be provided with a shoulder15. Or asshown in Fig. 13, the upper lap may have a shoulder 16 and thelower lap a shoulder 17.

In Fig. 14, the lower lap is shown as provided with a shoulder 18, soshaped as to lap on its upper surface 19, the lower end of a coneroller, such as are used in roller bearings, the upper lap having aproperly shaped shoulder 20.

The purpose of these shoulders, whether one or'more than one is used, isto limit the movement of the article in the direction of its own axis.

These shoulders are particularly desirable when frusto-conical articlesare being lapped, and have the particular advantage that in addition tothe accurate finishing of the conical' surface, the end-portions orbutts of the frusto-conical articles are simultaneously lapped to theexact desired relation between i the diameter of the butt portion andthe longitudinal dimensions ofthc cone. Ry the use of properly shapedshoulders on one or both laps, any of the many shapes of cone.- rollersnow commonly used may thus be brought to exceedingly accurate dimensionsand to the shape desired for use. It is not essential that both lappingsurfaces should be surfaces of revolution. As shown in Fig. 15, one ofthe laps, e. g. the lower lap, may be a plane surface, and the other ahyperboloidal or other suitable .surfacel of revolution. l

The work holder 8 may consist (as shown in Figs. 4 and 5) of a suitabledisk-shaped device having an upturned rim with openings 12, 12corresponding in shape to the article being ground; or if the article,such as a wrist pin, is hollow, the work carrier disk may havesupporting pins 14, 14 eX- tending into the holes in the wrist pins. Inany case, the work holder acts as a guide to hold the articles at theproper angle of inclination, the articles being otherwise free to moveunder the influence of the laps.

In the construction shown in Fig. 1, the floating lap is self-centering,but in other forms of the device it may be necessary to provide meansfor centering the revoluble While my invention is mainly designed forbringing articles of the kind described to a final exceedingly accurateform or contour by the use of lapping surfaces, it is obvious Vneeaevathat the same princi les apply to coarser grinding by the use o othercommonly used abrasive surfaces.

/While I preferably make one of the laps freely floating, so that it canadjust its position4 and rest upon the articles belng abraded, thisconstruction is not strictly es sential, as even if the revoluble lap bemounted on a fixed axis, results sufficiently accurate for commeigcalpurposes may be obtained.

I claim:

l. The method of grinding articles having curved surfaces which consistsin subjecting said articles to abrasion between re1- atively movingabradin surfaces at least one of which is a curve surface of revolutionhaving the characteristic that through any pointof the surface tworectilinear surface elements may be drawn.

2. The method of grinding articles having curved surfaces which consistsin subjecting them to abrasion between grinding means at least one ofwhich has a hyperboloidal surface of revolution.

3. The method according to claim 1 in which the grinding means are lapsone of which is non-rotatable and the other is rotatable, one ofsaidlaps being' freely floating.

4. An apparatus for grinding articles comprising one non-rotatable lapand a cooperating rotatable lap, said la s having abrading surfaces atleast one o which is a surface of double curvature yhaving thecharacteristic that through any point of the surface two rectilinearsurface elements may be drawn, and means for rotating said rotatable ylap.

5. `An apparatus for grinding articles comprising one non-rotatable lapand a cooperating rotatable lap, said laps=having abrading surfaces atleast one of which is a hyperboloid of revolution, and means forrotating said rotatable lap.

6. An apparatus as claimed tin claim 4 having a work holder foi"articles to be ground between the laps, said `holder having beingground, and a work holder having means for holding the articles at aproper inclination.

8. An apparatus for grinding articles as claimed in claim 4 having aWork holder for articles to be ground between the la s, said holderhaving means for holding t e articles at the desired angle and inwhichone of the laps is freely floating.-`

9. An apparatus for grinding articles having curved surfaces, such ascones or cylinders, comprising one lap having' a hyperboloid surface ofrevolution, a cooperating lap having a corresponding hyperboloid surfaceof revolution, a work holder having means for holding the articles whilebeing ground between such lapping surfaces at such angle that generatinglines on the surfaces of the articles will coincide with generatinglines on each of the hyperboloid lapping surfaces, and means forrotating one of said laps.

10. An apparatus as claimed in claim 9 in which the la s are positionedone above the other, one o such laps arran ed to be nonrotatable and theother to be reely floatin said upper lap having a shoulder surroun ingthe grinding surface and adapted tobear on the articles being ground.

11. An apparatus for grinding articles having curved surfaces comprisinga pair of laps one of which is revoluble, said laps having abradingsurfaces at least one of which is a hyperboloid of revolution, a workholder having means for holdin the articles while being ground at theesired an le, and means comprising a shoulder or s oulders for limitingthe movement of the articles being ground in the direction of theiraxes.

12. An apparatus for grinding articles iting the movement of thearticles bein ground in the direction of their axes, sai means havingabrasive surfaces of the pro er shape to accurately form the surfaces oft ose portions of the articles with which they engage.

In testimony whereof,

I aix my signature.

WILLIAM E. HOKE.v

